1. Field of the Invention
The present disclosure relates to a voice coil motor.
2. Description of Related Art
Recently, various optical devices including mobile phones embedded with a super small digital camera and high resolution digital cameras have been developed. The super small digital camera embedded in the conventional mobile phone currently cannot adjust a gap between an image sensor and a lens. However, such a gap between an image sensor and a lens may be adjusted by a lens driving device such as a voice coil motor.
Related art voice coil motors (VCMs) generally include a base and a movable body coupled to the base. The movable body includes a bobbin accommodating the lens of the camera and a coil wrapping the bobbin. The VCM further includes a stator including a long magnet and a housing wrapping a yoke fixing the magnet. The magnet is arranged at a periphery of the movable body to face the movable body by the yoke fixing the magnet. Pan springs are arranged on an upper surface and a bottom surface of the movable body to resiliently support the stator and a spacer is arranged between each pan spring and the stator. A case surrounds the components of the VCM.
The VCM thus configured allows a gap between an image sensor and a lens to be adjusted by using electromagnetic force lines generated by the coil, and attractive force and repulsive force from electromagnetic force lines of the magnet facing the coil.
However, there is a disadvantage in using a long magnet because the long magnet fixed at the yoke is a high-priced sintered magnet and should be cut into several pieces that are, in turn, attached to the yoke, thereby consuming many hours for assembling the magnets and yoke and increasing the manufacturing cost.
Another disadvantage is that the manufacturing cost can be expensive because many elements of the VCM such as the yoke, housing, and spacer are employed for blocking the electromagnetic field generated by the coil and the magnet and for fixing the magnet. This component arrangement is similar to a spindle motor. However, the assembling processes of a spindle motor for the voice coil motor are complicated, increasing the assembling time and decreasing the productivity of the product.
Still another disadvantage is that it can be difficult to accurately control assembly allowances for the elements of the VCM when the VCM includes elements such as the yoke, housing, and spacer that are employed for blocking the electromagnetic field generated by the coil and the magnet and for fixing the magnet.